JPH10125831A - Heat sink radiation fin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sink radiation fin which is easily machined at fabrication, light in wt. and usable by directly mounting it on a chip. SOLUTION: A fin comprises a flat bottom plate 30 and a radiator 9 disposed on one side thereof. The radiator is made of Al, and flat bottom plate is a clad plate having an Al layer and metal layer having a low linear expansion coefficient. At least the lower face of the bottom plate 30 is an Al layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink radiator fin (hereinafter referred to as a radiator fin) mounted on an LSI (Large Scale Integrated Circuit) chip for cooling the chip.

[0002]

2. Description of the Related Art An LSI package (hereinafter simply referred to as a package) is the most basic electronic device containing a chip.

FIGS. 4A and 4B show an example of a typical plastic ball grid array type package (hereinafter, referred to as a BGA package), wherein FIG. 4A is a cross-sectional view and FIG. The chip 2 is bonded to the epoxy resin plate 1,
Solder balls 4 serving as external terminals on chip 2 and resin plate 1
Are electrically connected via a bonding wire 5 and a conductive circuit (not shown) on the resin plate 1, and are entirely sealed with the epoxy resin 3. The solder ball 4 is shown in FIG.
As shown in FIG. 2B, they are regularly arranged on the lower surface of the resin plate 1 and mounted on a printed circuit board (not shown).

Meanwhile, the degree of integration of chips has been improving year by year in order to improve the processing speed, and at the same time, problems such as malfunction due to heat generation of the chips and breakage of the package have become a problem.

The most widely adopted measure for suppressing the temperature rise of the chip is to mount heat sink fins on the package and remove the heat from the chip by natural air cooling or forced air cooling by a fan.

FIGS. 5 to 7 show typical examples of the radiation fins.

FIGS. 5A and 5B show an example of a channel type heat radiation fin 6 (hereinafter, referred to as a channel fin), wherein FIG. 5A is a plan view and FIG. 5B is a front view. The height h that becomes the heat radiation part,
A number of heat radiating plates 6a having a thickness t are provided vertically with a gap g in a bottom plate portion 6b having a thickness T. Plane dimension W of bottom plate 7
₁ × W ₂ is usually substantially the same as the planar dimension of the package.

FIGS. 6A and 6B show an example of a pin-type heat radiation fin 7 (hereinafter, referred to as a pin fin), wherein FIG. 6A is a plan view and FIG.
Is a front view. A large number of radiating pins 7a having a height h and a thickness d ₁ × d _{2 serving} as radiating portions are provided with gaps g ₁ and g _{2 in} the bottom plate 6 having a thickness T.
Standing vertically in the. The cross section of the heat radiation pin 7a may be circular or the like.

FIG. 7 shows an example of a corrugated radiating fin 8 (hereinafter referred to as a corrugated fin) described in Japanese Patent Application No. 7-91525. FIG. 7A is a plan view, and FIG. It is. A thin wave-shaped heat radiation plate 8a serving as a heat radiation part and a bottom plate 8b are joined by brazing. Aluminum or an aluminum alloy (hereinafter, both are collectively referred to as aluminum) is generally used as a material of these heat radiation fins from the viewpoint of lightness, economy, and the like. Are collectively referred to as copper).

FIG. 8 shows a BGA with pin fins 7 attached.
1A shows an example of a package 10, in which FIG.
Is a plan view. The pin fins 7 are joined to the upper surface of the epoxy resin plate 11 of the BGA package by a heat conductive adhesive layer 14. The chip 2 is bonded to the lower surface of the resin plate 11 with a heat conductive adhesive layer 16, and a through hole called a thermal via 15 buried with solder or the like is provided in a chip mounting portion of the resin plate 11. The chip 2 and the solder balls 4 serving as external terminals on the resin plate 13 are electrically connected via bonding wires 5 and conductive circuits (not shown).
The inside of the frame-shaped epoxy resin plates 12 and 13 in which is stored is sealed with an injected epoxy resin 17. The heat from the chip 2 is transmitted to the bottom plate 6 through the thermal via 15,
The heat is radiated from the heat radiation pin 7a.

FIG. 9 shows another B having pin fins 7 attached thereto.
7A shows an example of a GA package 18, and FIG.
(B) is a plan view. The pin fins 7 are joined to the upper surface of the heat spreader 19 of the package 18 by a heat conductive adhesive layer 22. The function of the heat spreader 19 is to transmit heat from the chip 2 to the pin fins 7,
It is made of copper or copper alloy having excellent thermal conductivity and is joined to a frame-shaped epoxy resin plate 20. The chip 2 housed inside the epoxy resin plate 20 includes a solder ball 4 as an external terminal on the lower surface of the frame-shaped epoxy resin plate 21 joined to the epoxy resin plate 20, a bonding wire 5, and a conductive circuit (not shown). ) And are sealed with the injected epoxy resin 23. A grease-like thermal compound 24 is interposed between the chip 2 and the lower surface of the heat spreader 19.

The use of the thermal compound 24
When the chip 2 is firmly bonded to the heat spreader 19 with an adhesive, the linear expansion coefficient (2 to 3 × 10
^This is because the difference between the linear expansion coefficient (about 17 × 10 ⁻⁶ / K) of the heat spreader 19 made of copper or a copper alloy is so large that the chip 2 is broken by thermal stress.
That is, the thermal compound 24 has a role as a buffer material for absorbing a difference in linear expansion. Of course, there is also a role of electrically insulating the metal heat spreader 19 and the chip 2. If the heat spreader 19 is made of tungsten impregnated with copper, the linear expansion coefficient (about 5 × 10 ⁻⁶⁾
/ k) comes closer to silicon and also has thermal conductivity.
It is known that chips can be directly joined to a heat spreader. However, since the specific gravity of tungsten (about 19) is extremely large and the weight of the package increases, it cannot be adapted to the trend of reducing the weight of electronic devices.
Another difficulty is that tungsten is difficult to process and cannot be manufactured economically. If the heat sink fins can be directly bonded and fixed to the chip, the number of components constituting the BGA package can be greatly reduced, and a small, high-performance fin can be realized.

FIG. 10 is a diagram showing the Ball Grid Array Technology (M
cGraw-Hill, Inc.) is a conceptual diagram of a BGA package 25 directly attached with a radiation fin 50 described on page 198. (A) is a sectional view, and (b) is a plan view.

The periphery of the chip 2 'housed in the package 25 is sealed with an epoxy resin 27, but the upper surface is exposed.
0 is joined. Pb, Sn on the lower surface of the chip 2 '
And a large number of bumps 29 of Au.

In contrast to the case of FIGS. 8 and 9, since the chip circuit is provided on the surface on the side to be bonded, it is also called a flip chip. The bump 29 is bonded to a connection terminal (not shown) on the upper surface of the epoxy resin plate 26. Since the wireless bonding, it is possible to reduce the shortening bonderizing _Lee ing time of transmission time. These connection terminals and the solder balls 4 on the lower surface of the resin plate 26 are electrically connected. Since bonding is performed using the entire lower surface of the chip 2 and the solder balls 4 can be arranged on the entire lower surface of the resin plate 26, the outer dimensions of the package 25 are smaller than those of the package 10 of FIG. It is also called a chip size package.

However, the BGA package with a heat radiation fin shown in FIG. 10 cannot be realized by using a conventionally known aluminum or copper heat radiation fin. That is, the difference between the linear thermal expansion coefficient of the silicon chip 2 'and the linear thermal expansion coefficient of the heat radiation fin 50 is large, and the chip is broken by thermal stress during use. Although it is possible to join the radiating fin 50 to the chip 2 ′ made of the above-mentioned copper-impregnated tungsten having a linear expansion coefficient equivalent to that of silicon, it is difficult to process the radiating fin 50, so that the radiating fin 50 having a shape excellent in heat radiation performance can be economically manufactured. Can not be manufactured in a special way. In addition, there is also a problem that a load is applied to the chip 2 'because the weight is larger than anything. Therefore, B in which a radiation fin is directly attached to such a chip
At present, the GA package has not been put to practical use.

[0017]

As described above, in a package in which a conventional radiating fin is mounted, a chip that generates heat and the radiating fin are not directly joined. That is, in the package 10 of FIG.
9, the thermal compound 24, the heat spreader 19, and the adhesive layer 22 are interposed in the package 18 of FIG. Package 10 shown in FIG.
In (2), a thermal via 15 in which solder or the like is buried in the resin plate 11 is provided for heat transfer, but the cross-sectional area is restricted, so that a large heat transfer area cannot be obtained. Further, since the double adhesive layer is provided, its heat transfer resistance is also a problem.

In the package 18 shown in FIG.
The heat spreader 19 made of copper or a copper alloy has a good heat transfer property, and the heat transfer area from the chip 2 can be increased, which is more advantageous than the package 10 of FIG. However, the thermal compound 24 whose primary purpose is to buffer the difference in linear expansion requires a thickness of at least 0.2 to 0.3 mm, so that the heat transfer resistance is inevitably increased to some extent. In addition, thermal compound 1
Since a strong bonding force cannot be expected from the material 5 itself, there is also a problem in terms of reliability of maintaining the heat conductivity stably for a long period of time. As described above, in the package in which the conventional heat dissipating fins are mounted, heat is transferred by interposing various elements between the chip and the heat dissipating fins, so that the cooling performance of the heat dissipating fins cannot be sufficiently exhibited. There was a disadvantage.

Further, the radiation fin which can be directly mounted on the package shown in FIG. 10 has not been put into practical use for the above-mentioned reason.

It is an object of the present invention to provide a heat sink fin which is easy to process at the time of manufacturing, is lightweight, and can be directly mounted on a chip for use.

[0021]

If the bottom plate of the radiating fin has a linear expansion coefficient close to that of silicon, and if a radiating fin that is easy to process and lightweight is developed, the chip can be made thin (0.1 mm).
Since it can be directly bonded to the radiation fins by the adhesive layer described below, extremely efficient cooling can be performed. Not only that,
The structure of the BGA package with heat radiation fins can be greatly simplified and downsized.

The present inventors have conducted various experiments and studies to develop such a heat sink fin and have obtained the following findings.

1) The material of the radiation fin is preferably aluminum from the viewpoints of workability, electric heat and weight. However, since the linear fin has a large linear thermal expansion coefficient, it is difficult to directly adhere to the radiation fin made of aluminum and use it. Can not. However, by making the bottom plate of the radiation fin a clad plate of metal and aluminum having a small coefficient of linear thermal expansion, the overall coefficient of linear expansion can be reduced, and chip breakage that occurs during use can be prevented. Further, by using a clad plate made of aluminum, the weight increase of the radiation fin is reduced.

2) In order to reliably electrically insulate the chip and the radiation fin, the lower surface of the bottom plate of the radiation fin needs to be made of an aluminum layer.

The present invention has been made based on such knowledge, and the gist of the present invention is a heat sink fin having a flat bottom plate portion and a heat radiating portion provided on one surface thereof. Wherein the flat plate-shaped bottom plate is a clad plate provided with an aluminum layer and a metal layer having a low linear expansion coefficient, and at least the lower surface of the bottom plate is an aluminum layer. Heat radiation fins "Here, aluminum refers to both pure aluminum and aluminum alloy. Further, the lower surface of the lower surface of the bottom plate portion indicates a surface opposite to the surface on which the heat radiating member is provided, and the lower surface portion indicates the vicinity of the lower surface including the lower surface.

Further, the expression that at least the lower surface portion of the bottom plate portion is an aluminum layer means that the lower surface portion of the bottom plate portion is always an aluminum layer, and its vicinity including the heat radiation side surface of the bottom plate portion as required (hereinafter referred to as the upper surface of the bottom plate portion). Means to be an aluminum layer. In order to prevent the chip from being destroyed by thermal stress, the present inventors set the linear expansion coefficient of the bottom plate of the heat radiation fin close to the linear expansion coefficient of silicon in order to directly join the chip to the heat radiation fin. I paid attention.

As described above, the coefficient of linear expansion of silicon is 2-3 × 10 ⁻⁶ / K. On the other hand, the linear expansion coefficient of aluminum or an aluminum alloy used for the radiation fin is about 23 × 10 ⁻⁶ / K, and the linear expansion coefficient of copper or a copper alloy is about 17 × 10 ⁻⁶ / K. The difference between the coefficients is too large. Therefore, 10-2
A chip of various sizes of 5 mm square is bonded and fixed to various metals having different linear expansion coefficients, and a thermal expansion test is performed in a temperature range from room temperature to about 150 ° C. at which a highly integrated chip is expected to reach. An experiment was performed on the critical coefficient of linear expansion that would not cause the fracture.

As a result, when the linear expansion coefficient is 9 × 10 ⁻⁶ / K or less, a chip up to 15 mm square is not broken, and when the coefficient of linear expansion is 7 × 10 ⁻⁶ / K or less, a chip up to 25 mm square is not broken. I found that it would not be destroyed. Next, a number of trial production experiments were conducted on the structure of the heat radiation fin, which has a low linear expansion coefficient as the bottom plate of the heat radiation fin and does not impair the lightness.

As a result, it has been found that desired characteristics can be obtained by forming a clad structure of aluminum and a metal having a small linear expansion coefficient. Of course, a combination of copper or a copper alloy with a material having a small coefficient of linear expansion is also possible, but from the viewpoint of reducing the weight of electronic components, a combination with aluminum was used.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, each condition defined in the heat sink fin of the present invention will be described.

1) Reason for using aluminum for the heat radiation member Aluminum is easy to process, has excellent heat conductivity, is lightweight and economical, and is a material suitable for heat radiation fins.
The heat radiation member was aluminum. Further, aluminum has an advantage that excellent corrosion resistance can be obtained by alumite treatment, and at the same time, a color tone such as black or white can be obtained.

2) The reason why the bottom plate is made of an aluminum layer and a metal layer having a low linear expansion coefficient is a clad plate. The lower surface of the bottom plate of the radiation fin, and if necessary, the upper surface must be an aluminum layer for the reasons described in 3) below. No. However, since aluminum has a large coefficient of linear expansion, a metal having a small coefficient of linear expansion and a clad plate are used so that the coefficient of linear expansion of the entire bottom plate is set to such a size that the chip is not broken by thermal stress.

The metal having a low linear expansion coefficient means that when the bottom plate portion of a clad plate of aluminum and a metal having a low linear expansion coefficient is used, the linear expansion coefficient of the bottom plate from room temperature to 150 ° C. is 9 × 10 ^−6. / K or less, preferably a metal that can be reduced to 7 × 10 ⁻⁶ / K or less. There is no practical problem if such a linear thermal expansion coefficient is set.

Needless to say, the risk of destruction disappears as the coefficient of linear expansion of the bottom plate approaches the coefficient of linear expansion of the chip.

In order to make the linear expansion coefficient of the entire bottom plate portion as described above, what should be the linear expansion coefficient of the metal having a low linear expansion coefficient depends on the thickness of the aluminum layer provided on the bottom plate portion. Since they are different, they are not specified.

In order for the linear expansion coefficient of the entire bottom plate portion to be at the above level, the metal having a low linear expansion coefficient constituting the clad plate needs to have a smaller linear expansion coefficient than that of aluminum. Needless to say. The smaller the coefficient of linear expansion of a metal having a low coefficient of linear expansion, the greater the ratio of the thickness of the aluminum layer to the thickness of the bottom plate portion, so that the total weight of the radiation fins can be reduced.

As a metal having a low coefficient of linear expansion, 35 to 36
An iron alloy containing Ni in the range of 36% by weight is preferable.
The average linear expansion coefficient of the alloy (Invar) up to 150 ° C. is about 1.2 × 10 ⁻⁶ / K, and the average linear expansion coefficient of the 36Ni-4Co—Fe alloy (Super Invar) up to 150 ° C. is about 0.6 ×. 10 ⁻⁶ / K.

In contrast to the conventional radiation fin, the radiation fin of the present invention has a low linear expansion coefficient metal layer between the radiation part and the chip. Has little effect.

3) The reason why the lower surface of the bottom plate is made of an aluminum layer The lower surface of the bottom plate is made of an aluminum layer because the alumite treatment enhances the corrosion resistance and at the same time, obtains the electrical insulation between the chip and the radiation fins. That's why.

Another object of the present invention is to suppress an increase in the warpage of the bottom plate, which is harmful to the chip, due to the thermal expansion of the aluminum radiator.

4) The reason why the upper surface of the bottom plate is also made of an aluminum layer if necessary The aluminum layer is provided on the upper surface of the bottom plate in order to impart corrosion resistance or color tone by alumite treatment. Further, depending on the balance between the linear expansion of the aluminum heat radiating portion and the aluminum layer on the bottom surface of the bottom plate portion, the bottom plate portion also has a role of suppressing warpage. When only the purpose of imparting the corrosion resistance or the color tone is intended, the upper surface of the bottom plate may not necessarily have the aluminum layer, and may be formed by, for example, painting.

When a heat dissipating member made of aluminum is brazed to the bottom plate to form a heat dissipating fin, it is easy to braze by providing an aluminum layer also on the upper surface of the bottom plate. In this case, an aluminum alloy brazing may be provided on the upper surface of the bottom plate, or may be a single-sided brazing sheet having a layer of aluminum brazing on the brazing surface of the heat dissipation member.

When it is necessary to adjust the color tone of the low expansion metal portion exposed on the peripheral edge of the bottom plate to another, a means such as a coating treatment may be taken.

The heat dissipating portion of the heat dissipating fin of the present invention may have any shape such as a pin fin, a channel fin, and a corrugated fin. In particular, corrugated fins are preferable because they are lightweight.

The method for producing the clad plate of the bottom plate is preferably a method in which aluminum and a low linear expansion metal are superposed and rolled hot or warm. This is because, by manufacturing in this way, metal diffusion occurs at the interface between the two metals, and the metal is firmly joined. Hereinafter, specific examples of the radiation fin of the present invention will be described.

FIG. 1 shows an example of a radiating fin according to the present invention. The radiating fin has a corrugated fin as a radiating portion, and an upper surface and a lower surface of a bottom plate are aluminum layers.
(A) is a plan view, (b) is a front view, and (c) is a bottom plate 3.
It is the elements on larger scale of 0.

The heat radiating portion is a corrugated fin 9 shown in FIG.
And the corrugated radiator plate 9 and the bottom plate 30 are joined by brazing. As shown in FIG. 1C, the bottom plate 30 has a structure in which upper and lower surfaces of the bottom plate are made of aluminum layers 32 and 33, and the low expansion metal layer 31 is sandwiched between these aluminum layers.

The total thickness (td '+ te') of the upper and lower layers 32 and 33 of the bottom plate, the linear expansion coefficient and the low expansion metal layer 31
The coefficient of linear expansion in the direction parallel to the lower surface of the bottom plate 30 can be adjusted by the thickness tc 'and the coefficient of linear expansion.

Since the bottom portion 9a of the corrugated heat radiating plate 9 is brazed to the aluminum layer 32, the bottom plate upper and lower surface layer layers 32, The ratio of the thicknesses td 'and te' of the 33 is adjusted. As described above, the upper and lower surface layers 32 and 33 are
The purpose is to impart corrosion resistance and electrical insulation to the surface of the bottom plate 30 by alumite treatment. Further, the upper surface layer 32 also has a role of brazing the corrugated heat sink 9 made of aluminum.

When the corrugated heatsink 19 can be directly brazed to the low expansion metal layer 31, the upper surface layer 32 is not always necessary, but a corrosion-resistant treatment may be required instead of the alumite treatment. When the upper surface layer (32) is used for brazing, it can be efficiently brazed by manufacturing it from an aluminum alloy braze. An aluminum alloy braze may be provided on the surface to be joined to the plate 9. Fig. 2 shows another example of the heat radiating fin of the present invention, in which a pin fin is used for a heat radiating portion. () Is a plan view, (b) is a front view, and (c) is a partially enlarged view of the bottom plate portion 34.
The pin fins are the same as the conventional pin fins shown in FIG. 6, and the heat radiation pins 8 made of aluminum are integrated with the bottom plate portion 34 and stand regularly.

As shown in (c), the bottom plate 34 has aluminum layers 36 and 37 on the upper and lower surfaces in the same manner as the radiation fins in FIG.
Is provided.

The temperature rise of the radiating fin due to the heat from the chip is large at the bottom plate portion, and the temperature of the radiating portion decreases from the root to the tip at the radiating portion. Therefore, the influence of the heat radiating portion on the linear expansion of the bottom plate portion is small, and it can be considered that the linear expansion coefficient of the bottom plate portion is substantially determined by the thickness and the linear expansion coefficient of each metal constituting the bottom plate portion. That is, in FIG. 2C, the total thickness (td + te) of the upper and lower surface layers 36 and 37 of the bottom plate portion, the coefficient of linear expansion, the thickness tc of the low expansion material metal 35 and the coefficient of linear expansion indicate the lower surface of the bottom plate portion 34. The linear expansion coefficient in the direction parallel to the part can be adjusted.

Note that the magnitude relationship between td and te is adjusted so that the bottom plate does not warp and deform when the temperature rises. If the heat radiation portion does not affect the warpage of the bottom plate, td = te may be used.

FIG. 3 is a view for explaining one method of manufacturing the heat radiation fin of the present invention. By manufacturing a clad material composed of three layers of aluminum 38, a low expansion metal 39, and aluminum having a thickness ta corresponding to the height of the pin fins, and forming a pin-shaped or plate-shaped heat radiation portion by cutting the aluminum 38. A radiation fin can be manufactured.

[0055]

Embodiment 1 FIG. 3 is a view showing a clad plate used in the present embodiment, in which a heat radiating portion is a material of a heat radiating fin composed of a pin.

As shown in FIG. 3, this material is a clad plate comprising three layers, an upper layer, an intermediate layer and a lower layer. The upper layer 38 and the lower layer 40 are made of a 3003 aluminum alloy specified by JISH4000.
The intermediate layer 39 is made of a super Invar alloy (36Ni-4Co).
-Fe). The thickness of each layer is as follows.

Upper layer (aluminum alloy): ta = 19.15 mm Intermediate layer (sub-inner alloy): tc = 0.7 mm Lower layer (aluminum alloy): te = 0.15 mm Total height: H = 20 mm By cutting from this material, FIG. A radiating fin having a height H = 20 mm having a square cross section and having a total height H of 20 mm was manufactured, and then subjected to an alumite treatment. The dimensions of the radiation fin were as follows.

Heat radiating pins (total 121) Thickness: d1 = 2 mm, d2 = 2 mm, Height: h = 19 mm Gap between pins: g1 = 3 mm, g2 = 3 mm Thickness of upper surface layer of bottom plate (aluminum alloy): td = 0.15mm Intermediate layer thickness (Super Invar alloy): tc = 0.7mm Lower surface layer thickness (Aluminum alloy): te = 0.15mm Plane dimensions: W1 = 42mm, W2 = 42mm 150 ° C with electric heater
And the coefficient of linear expansion in the direction parallel to the bottom surface of the bottom plate was found to be 4.8 × 10 ⁻⁶ / K.

Next, a silicon chip of 25 mm square and 0.5 mm thickness is adhered to the lower surface of the bottom plate portion 34 of the heat radiation fin, and the chip is heated to 150 ° C. by an electric heater and 20 ° C. by forced air cooling. Cooling was repeated 50 times.

No cracks were observed in the subsequent chips.

The weight of the heat radiation fin was 36.4 g.
Thus, the increase of the heat radiation fins was only about 7 g compared to the case where the entire heat radiation fin was made of 3003 aluminum alloy (weight 29.6 g). (Example 2) A corrugated fin 9 shown in FIG. 1 was manufactured using a 3003 aluminum alloy thin plate having a thickness t = 0.3 mm. However, the number of mountains was nine. The dimensions of the fin were as follows.

Pitch: p = 4.2 mm Gap: g = 1.8 mm Height: h = 8.3 mm Thickness: t = 0.3 mm As a bottom plate, an invar alloy (36N) having a thickness tc = 1.0 mm
The clad plate provided with an i-Fe) layer, a 3003 aluminum alloy layer having a thickness of te '= 0.3 mm, and an aluminum alloy brazing layer defined by JISZ3263 having a thickness of td' = 0.1 mm can be easily formed into a bottom plate having a total thickness of T = 1.4 mm. The corrugated fin was vacuum brazed at a temperature of 580 ° C.

Thus, the plane dimensions W1 = 40 mm, W2 =
A heat radiation fin having a corrugated fin having a height of 40 mm and a total height H of 9.7 mm was manufactured and subjected to anodizing.

The bottom plate of the radiating fins is
After heating to 0 ° C., the coefficient of linear expansion in the direction parallel to the bottom surface of the bottom plate was found to be 4.1 × 10 ⁻⁶ / K.

Next, the bottom plate of the radiating fin is
A silicon chip having a square shape of 0.5 mm and a thickness of 0.5 mm was adhered, and heating to 150 ° C. by an electric heater and cooling to 20 ° C. by forced air cooling were repeated 50 times.

No cracks were observed in the subsequent chips.

The weight of the radiation fin was 15.1 g.
Therefore, the increase was only about 9 g from the case where the whole was made of a 3003 aluminum alloy (weight 6.2 g).

[0068]

According to the present invention, the radiating fin having the bottom plate portion of the clad plate obtained by combining the aluminum and the low linear expansion metal,
Since there is no breakage of the chip during use due to the difference in the coefficient of linear expansion between the bottom plate and the chip, the chip can be directly bonded to the silicon chip and has excellent heat dissipation. In addition, since the chip surface can be exposed from the package and the radiation fins can be directly bonded to the chip surface, the package can be simplified and reduced in size. Since the heat radiating portion is made of aluminum, which is easy to perform plastic working or cutting and is lightweight, a shape excellent in heat radiating performance can be freely set. Further, since the heat from the chip is efficiently transmitted to the radiation fins, the cooling performance of the radiation fins can be sufficiently exhibited. As a result, the radiation fin itself can be reduced in size. With the increase in the degree of integration of chips and the resulting increase in the amount of heat generated, electronic devices must be further reduced in size and weight in the future. The radiation fin of the present invention has a great effect on such needs.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a heat radiation fin of the present invention.

FIG. 2 is an explanatory diagram showing another example of the present invention.

FIG. 3 is an explanatory view of a material for manufacturing a radiation fin.

FIG. 4 is a view of a conventional plastic BGA package without using a radiation fin.

FIG. 5 is a view of a conventional channel-type radiation fin.

FIG. 6 is a view of a conventional pin-type heat radiation fin.

FIG. 7 is a view of a corrugated heat radiation fin.

FIG. 8 is a view in which a conventional heat radiation fin is attached to a plastic BGA package.

FIG. 9 is a diagram showing another example in which a conventional radiating fin is attached to a plastic BGA.

FIG. 10 is a conceptual diagram of a BGA package in which heat sink fins are directly attached to a package.

[Explanation of symbols]

 1, 11, 12, 13, 17, 20, 21, Epoxy resin plate 2 Chip 4 Solder ball 5 Bonding wire 6 Heat sink 7 Bottom plate 8 Heat sink pin 9 Corrugated fin 14, 16, 22, 28 Adhesive layer 15 Thermal pier 19 Heat spreader 24 Thermal compound 25 Package

Claims (1)

[Claims] A heat sink fin having a flat bottom plate portion and a heat radiating portion provided on one surface thereof, wherein the heat radiating portion is made of aluminum, and the flat bottom plate portion has an aluminum layer and a low linear expansion coefficient. A heat dissipating fin, wherein at least the lower surface of the bottom plate is an aluminum layer.